Catadioptric unit



Oct. 12, 1937. c. w. FREDERICK ET AL 2,095,862

1 CATDIOPTRIG UNIT Filed Ju1y 11, 1934 1111. Apkermzswfeabymmew man@ Swfamybmumd) l wuwtome mzasmmdermmmm W. mw

55 example, the surface may be provided with hap- Paienied on. 12, 1937 2,095,862

UNITED STATES PATENT ori-ICE c oATAmoP'rmc UNrr Charles W. Frederick.' Rochester, N.

Richard Luce, Elizabeth, N. J., assignors, by mesne assignments, to Eastman Kodak Company, Jersey City, N. J., a corporation of New Jersey g Application July 11, 1934, Serial No..734,646 2 Claims.- (Cl. 8882) vThis application is a continuation in part of hazard minute indentations in the nature of an our copendlng application Serial No. 644,802, orange peel effect. led November 29,1932. (Patent No. 2,073,300) We have found that roughening of the surface which in `turn is a continuation in part of our of the lens molding tool with a certain grade of 5 application lSerial No. 635,034, filed September emery powder toproduce the orange peel eiect 27,1932. upon the lens will produce'a lens in which the The present invention relates to a catadioptric roughened surface will tend to reunite the varilmit f the type knOWn In the trade as a reilector ous colors into White light. 'I'his treatment of button. The general objects of the invention themold imparts t0 the surface 0f the lens a degree of -relatively minute intermittent deviaare fully stated in the parent application and the present appucatin relates to that specific tion from the theoretically correct contour of the lens. The mold may be treated in various ways embodiment of the invention which-is generically claimed in th parent application; in which one and the precise manner in which itis done forms of the surfacesis rendered light diffusing by hapno perf' of the invention herem elalmed Al' hazard deviations from a true surface, to intromatwely the heb used for formule the mold duce diffusion to a -controlled extent sufficient may be provided with the desired roughness I This hob is then used to sink the mold and the only to accomplish the *results desired as muy lenses molded therein will have the particular explained in the perent application' shape of the surface produced on the hob'.

By our invention-as muy explained in the It will be obvious that these minute irregupa'rent application' We prende e* simple ex' larities or optical inaccuracies in the surface of pement coincidentally to obtain the following the lens form a member of exceedingly small reand ether 'desired'resultsr namely', an .absence fracting surfaces which serve to mix or diffuse O f obleetienable' chromatic effect Just the de' the chromatically separated light emerging from sired amount of concentration of the emergent 1ah@ lens beam for axially incident light and for various The fimction of the irregular surface or sup angles of eeliqueness and anobnque beam of faces is to introduce a specific amount of consubstantially circular Shape in cross section' trolled diffusion, which acts to mix or reunite the For the purpose of this specification axially various Wave lengthsof the light separated by incl-dent light Shan mean that the light falling the chromatic .aberration of the lens, and also on the reecung mit is comme from@ source to impair lthe sharpness of the focus and hence located substantially on the axis of the unit and d th d ired increase in spread of the light reflected axially or "along the axis shall prov e e es emergent beam centered on the axis and to conmean that the reflected light, or cone of light, is trol and modify the character of the beam substantially centered on the wenn? theeumt obllquely in the respectsabove referred to.

In brief, in accordance with our invention, the complete or partial correction of a simple lens for spherical abberation by any of the several Well known methods is impaired so as to al'ord the desired spread of the axially reflected beam and in combination with the unavoidable oblique aberrations, coma and astigmatism, inherent in all lenses of the corrected type, to produce a beam of more regular shape in cross section and with a controlled amount of divergence, which divergence increases coincidentally with the increasing angle of obliqueness. This impairment is accomplished by an expedient which results in integration of the chromaticallyseparated `light sound, therefore, in an absence of' the chromatic effect. This expedient may conveniently be the providing of the reflecting surface with a relatively minute intermittent deviation from thetheoretically correct contour of the surface. For

will appear from the following description when read-in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

Fig. 1 is a central axial section of an embodiment of our invention having a double convex lens the rear surface of which is reflective.

Fig. 2 is a similar view of' a unit in which the reector is separated from the lens.

The reflector buttons illustrated in the drawing and described below comprise a reflector posi-'- tioned approximately in the focal plane of a collecting lens whereby a distant source of light is imaged on the reector and the light is reflected back toward the source as is well known.

'I'he unit shown in Fig. 1 consists of a single uniy tary lens 50, the rear surface 5I of which is spherical and backed with a, reflecting layer 52 of Other details and advantages of our invention silver, which in turn may be backed by ya protective and supporting layer 53 of copper or other metal. The front surface 5I is convex and aspherical in form and so designed as to correct the lens for spherical aberration as is well known. lIn accordance with our invention the refracting surface 54 or the reflecting surface 5i is haphazardly roughened a slight .amount so that the cones of differently colored light which would normally be formed by the chromatically uncorrected lens will be diffused and mixed to such an extent as to be indistinguishable and the reflected light will appear substantially white to ,an observer irrespective of his location so long as he is within the eld of divergence of the returned light.

One way in which the roughening may be applied to the surfaceand particularly to the rear surface 5l of a lens such as in Fig. 1, where it is curved and constitutes the reilecting surface, is to form iirst a spherical mold, then roughen this with an emery powder which will form in the mold roughnesses greater than are finally desirable in the lens surface. When this mold is used with buttons of heated and softened, but not molten, glass, the softened glass does not entirely flll the interstices between the rough particles of the mold but forms minute lenticular convexities in the surface of the glass. The resulting diifusing surface is one which can be reproduced and is distinctly different from the inaccurate surfaces ob-` tained heretofore by pot molding due to slumpage and the like. The slumpage inaccuracies were not only unpredictable and non-reproducible but generally diifered greatly in different lenses. By using molds pro-vided with the desired roughness and the so-called cane molding process, an accurately reproducible diffusing surface is obtained. When this is vsilvered, it forms a reticulated reflecting surface introducing the desired diffusion. The` size of the depressions in the reflecting surface should not be greater than the size of the image of a distant light source falling thereon.

In Fig. 2, the reflector is shown as separated from the rear surface 6| of the lens'62 and in this case any one of the surfaces may have a haphazard roughening. The lens has an aspherical front surface 64. In general the reflector would have a shorter radius of curvature than the surface 6 i.

The theory of the effect produced is sufficiently explainedin the parent application. The present embodiments are included in the scope of the parent application but the invention herein claimed is limited to the specific embodiments in which the limited amount of diffusion or scattering of the rays, sufficient to smother the effect of chromatic aberration but insufficient to increase substantially the angle of the reflected beam of light, is of a systematic nature.

Having thus described our invention, what we claim as new and desire to be secured by Letters Patent is:

l. An autocollimating catadioptric unit comprising the combination of a collecting lens substantially corrected for spherical aberration and uncorrected for chromatic aberration anda reflector behind the lens, at least one optical surface of the unit being accurately reproducible and differing from a single optical surface by relatively minute haphazard deviations of such a size and distribution that chromatic aberration is rendered imperceptible without substantially influencing the correction for spherical aberration.

2. An autocollimating catadioptric unit comprising the combination of a collecting lens substantially corrected for spherical aberration and uncorrected for chromatic aberration and a reflector behind the lens, the rear surface of the haphazard and not of a ,lens differing from a single optical surface by relatively minute haphazard deviations of such a size and distribution that chromatic aberration is rendered imperceptible without substantially influencing the correctionfor spherical aberration. I

CHARLES W. FREDERICK. RICHARD W. LUCE. 

